R1 rear end ratio??

[B85]

Hello.
What would be the best Ratio Be?
3.364
3.545
3.70
3.90
4.11
What my plan is to build a full body Lotus 11.
Using A R160 rear end from a JDM Sti.
Just looking for some input.
Thanks, Randall

[B85]

So!!!
the 3.7 would put first gear at 58 with a top end 130 at WOT.
This is close to the Lotus 11 top end in its day.
Will the trans in the R1 be up to this?

[airframefixer]

What tire diameter will you be using? also depends what youre after? I know that a 4.1 diff with 22.7 inch tires will net approx 108 mph, good for accelerating but maybe not so comfortable for highway use. Id chose a diff that you know that you can get different ratios for.

[B85]

The tires will be ? if I can get them under the body will be the 225/50/15.
This maybe pushing things,maybe the 205/50/15 will be the best?
The old body will be here next week.It is a old CMC that never was mounted.Then it will be some fitting and then a new mold.

[Miatav8,MstrASE,A&P,F]

225/25.4=8.58+15=23.58" TD

Need the gear ratios in each gear, the primary reduction ratio between the trans and crankshaft, secondary reduction (chain and sprocket ratio), bike rear tire size, octane requirement, fully loaded weight and dry weight.

It is track only? Does it need to crawl in traffic at 3 mph? Highway cruising speed?

Intermediate drive is chain or driveshaft? If chain, what ratio?

[B85]

1000Lbs. + Driver 180Lbs

Prim = 1.581

1=2.5 =(1)=3.9525 58 mph wot 12,000rpm
2=1.842 = (2)=2.9122 79
3= 1.5 = (3)=2.3715 97
4=1.333 =(4)=2.1074 109
5=1.2 =(5)=1.8972 121
6=1.7628 =(6)=1.7628 130

Alum drive shaft
Track only

[Miatav8,MstrASE,A&P,F]

I guess your donor came with a 190-50-17 (24.48").


24.48 x 12,000 = 293760

1.581 x 1.7628 x 336(constant) = 936.43:1

293760/936.43 = 313.70

313.70/130 = 2.41 intermediate ratio (chain and sprocket)

2.41 x 1.581 x 1.7628 x 336 = 2256.79:1 overall ratio in sixth. It is approximate since I only carried it out two decimal places.

For a 23.58 tire to turn the motor to 12,000 rpm in sixth at 130 mph without the chain reduction:

23.58 x 12,000 = 282960/130 = 2176.62

2176.62/936.43 = 2.32:1 differential ratio for the same speed as the bike in each gear.

With a 3:364 diff,
3.364 x 336 x 1.581 x 1.7628 = 3150.14
282960/3150.14 = a top speed of 89.8 mph at 12,000 rpm in sixth.

With a 3.08 diff,
3.08 x 336 x 1.581 x 1.7628 = 2884.20
282960/2884.20 = 98.11 mph.

[B85]

Thanks.
I must be missing somthing??
Using the bike trans numbers=
First Gear 2.5 x the prim of 1.581=3.9525 ??
2= 1.842x PR= 2.9122 ??
3=1.5 x PR= 2.3715 ??
4=1.333x PR=2.1074 ??
5=1.2 x PR=1.8972 ??
6=1.115 x PR=1.7628 ??
I used this ?

http://www.catherineandken.co.uk/sti/tyres.html
Tires = 255/50/15
Rear Ratio = 3.7 to 1

And came up with this=
1= 58 mph
2= 79
3= 97
4= 109
5= 121
6= 130

Did I make a mistake??

Randall

[Miatav8,MstrASE,A&P,F]

I didn't realize you already multiplied the PR.

255-50-15 = 25.04" x 12,000 = 300472.441
3.7 x 336 x 1.7628 = 2191.513

300472.441/2191.513 = 137.11 mph at 12K in sixth.

I punched this into that program and got 137 mph in sixth.

[B85]

Thanks for the input!!!
I must not be looosing IT?

I am new to the Bike motor and was not sure if I had made a mistake.

Thanks again!
Randall

[Miatav8,MstrASE,A&P,F]

I don't think I answered your question though.

Consider the extra weight to be like towing a trailer.

I will assume the bike weighs 380 lbs, requires 92 octane, and is tuned to carry two 180 lb people without detonation under most conditions.

The design weight (gross) would be 740 lbs.

The locost will be 1180 lbs which is 1.59 times the design weight, a 59% increase. If you decide to have a passenger later, with two people onboard, it would be 1360 lbs and 1.84 times the design weight, a 84% increase.

A single occupant in a 1000 lb locost is equivalent to two R1 riders towing a 440 lbs trailer.

Two occupants in a 1000 lb locost is equiv to two R1 riders towing a 620 lb trailer.

If the bike will not detonate at gross on less than 92 octane, then there is a buffer and the load can increase somewhat without detonation if 92 is used.

For a single occupant, a 1.59:1 gear reduction would keep the load on the engine the same as it was designed for at gross, 740 lbs.

For two occupants, the ratio would be 1.84:1.
--------------------------------------------------------
Now to figure out the other changes.

The tire change is decreasing the gear reduction and increasing the load, going from 24.48" to 25.04". Think of this like a wrench attached to the axle, where the wrench handle has been lengthened .28" (half the tire diameter increase). When the lever is increased, the leverage the ground has to resist the rotation of the axle increases.

The 2.41:1 chain system is replaced with a 3.70:1 diff, increasing the gear reduction and decreasing the load. This is a gear reduction increase of 1.29:1. What you really want is 1.59-1.84:1 IF the top speed is adequate, 92 octane is required stock, 92 octane is the highest octane you plan to use and there is little or no detonation buffer stock.

A 4.00:1 diff will give you 126 mph and keep loading close to stock. Durability of the bike drivetrain should be close to stock.

[B85]

Good point!

I was looking at the power the car had when new.
1097 cc
83 Hp at 6800
75 T at 4400
Rear Ratio 4.22
Road & Track test Lbs. 1360

Do you know if 105 fuel will work with the PCM?
Randall

[Miatav8,MstrASE,A&P,F]

As long as it isn't aviation fuel it should be adequate, where even the "low lead" has a lot more in it than auto fuel ever did. If it does not detonate on 92, don't use a higher octane than necessary if your not adjusting the pcm to take advantage of it. Higher octane fuels burn at a different rate, which causes the flame front to travel across the chamber at a different rate. Try to use the octane the engine is tuned(by the pcm) to use if the loading is close. 92 may be okay. Other bec guys don't seem to have any problems when not matching the stock bike load exactly.

[B85]

OK! So the Bike PCM will not tune like my JDN Sti?
The Sti. took about 30 to 45 miles to see the better fuel.
Higher grade fuel the slower the burn! Less BTU's also!
Thanks for the input!!

Randall

[tigris]

Which Suby has a 3.3 rear?